It depends. If you've already spent a lot of time building in Unity (and haven't released yet), you'd have to redo a lot of code to port to Godot. It may make sense to launch with what you have and just explore Godot for future projects. However, Godot is about the most productive I've been in a long time, even after trying Unreal/Unity and various other engines. It's very natural to work, and things mostly make sense.
I wouldn't worry about performance too much unless you are making a serious 3D game. Unreal and Unity do have the upper hand with realistic graphics (in 3D) but you can still make something nice in Godot with a little work. For 2D, I would say Godot is the best, it's very easy to work with.
You can have IAP and ads, but I don't believe they are included by default. However, there are several 3rd party plugins you can use, it shouldn't be too hard (though I haven't tried this yet). But that is one area where Unity may be more robust.
In any case, I would just recommend downloading Godot and trying a simple project like Pong. I think you will see it is very user friendly. The editor loads fast, builds are fast, you can test on mobile and edit things and see your changes on the phone in real-time. It's very nice.